The present invention relates to a thread-milling cutter, which includes a cutting head with a number of cutting insert pockets, a number of thread-milling inserts, which are received in said cutting insert pockets and an attachment integrated with the cutting head, which is intended to be received in a tool coupling. The invention also relates to a thread-milling insert, which is mounted in the thread-milling cutter.
Through U.S. Pat. No. 5,873,684 a thread-milling cutter is previously known, which discloses a tool head, which is provided with a number of cutting insert pockets for receiving a corresponding number of thread-milling inserts. The thread-milling inserts are fixed in their cutting insert pockets by providing the inserts and associated cutting insert pocket with axially extending grooves. After a cutting insert is mounted in its cutting insert pocket, when said grooves are aligned with each other, a locking pin is inserted into the substantially cylindrical space which is defined by said grooves. Thereby the position of the cutting insert is fixed in the cutting insert pocket. The locking pin is secured by screwing locking screws into threaded holes in the milling cutter body, said holes terminating in the area of the groove in the milling cutter body.
The mounting becomes long-winded by the use of a locking pin for each cutting insert. Furthermore no satisfactory radial positioning of the locking pin is obtained since the locking pin cooperates with the groove of the cutting insert pocket, i.e., it is not probable that the effect of the locking screws on the locking pin bring about that the cutting insert abuts against the bottom of the cutting insert pocket. In addition at large radial cutting forces it can be a risk that the cooperation of the locking pin with the grooves in the cutting insert and the cutting insert pocket does not give a sufficiently exact positioning of the inserts in the radial direction, i.e. a certain dislocation of the inserts in radial direction may occur.
In the threading cutter according to U.S. Pat. No. 5,873,684, each threading insert has only one cutting edge and the cutting insert is provided with a clearance in connection with the cutting edge.
A primary object of the present invention is to provide a thread-milling cutter of the above-defined type, which is provided with a number of thread-milling inserts which are fixed in their respective associated cutting insert pockets in a constructively outstanding and simple manner but still satisfactory functionable.
Still another object of the present invention is to provide a thread-milling cutter wherein the positioning of the thread-milling inserts in the radial and axial directions is extraordinarily distinct.
Still another object of the present invention is to provide a thread-milling cutter having parts that require a small space, and therefor tools of small dimensions can be provided with more cutting inserts than prior art tools of corresponding dimensions.
Still another object of the present invention is to provide a thread-milling insert that exhibits a long life span.
One or more objects of the present invention are realized by a thread-milling cutter which comprises a tool holder and a plurality of thread-milling inserts mounted in the tool holder. The tool holder defines an axis of rotation and includes a cutting head and an integral attachment portion adapted to be received in a drive member. The cutting head includes a plurality of pockets extending generally axially in the cutting head, at least one screw-threaded hole communicating with each pocket, and a screw mounted in each hole for adjustment toward and away from the respective pocket. Each of the thread-milling inserts includes a securing portion received in a respective one of the pockets. The securing portion includes an abutment surface arranged to be pressed by one of the screws. The abutment surface forms an acute angle with a longitudinal center plane of the insert. The angle is oriented so that a pressing force transmitted from the screw to the abutment surface includes a component tending to push the insert in a generally radially inward direction within the respective pocket.
The invention also pertains to a thread-milling insert which comprises a cutting edge, a securing portion adapted to be mounted in a tool holder, and an underside. The securing portion includes an abutment surface disposed between the underside and the cutting edge. The abutment surface forms an acute angle with a longitudinal center plane of the insert, wherein the abutment surface diverges from the center plane in a direction toward the underside.